Travis CI: Add Python 3.7 to the testing

cclauss · web-flow · commit 3b43801067c8 · 2019-01-09T19:52:56.000+01:00
Also, [Travis are now recommending removing the __sudo__ tag](https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration).
diff --git a/.travis.yml b/.travis.yml
@@ -1,14 +1,17 @@
 language: python
 
-sudo: false
-
 python:
   - '3.5'
   - '2.7'
   - '2.6'
   - '3.4'
   - '3.6'
 
+matrix:
+  include:
+    - python: '3.7'
+      dist: xenial  # required for Python >= 3.7 (travis-ci/travis-ci#9069)
+
 install:
 - pip install -e .
 - pip install -r requirements-dev.txt
